An antenna used by a base station, including a relay, in a wireless communication system may have various shapes and structures. Recently, in a wireless communication antenna, a dual-polarized antenna structure has been generally used by applying a polarization diversity scheme.
Usually, a dual-polarized antenna has a structure in which four radiation elements having the shape of a dipole, as one radiation module, are properly arranged, in the shape of a tetragon or in the shape of a rhombus, on at least one longitudinally upright reflector. The four radiation elements, for example, radiation elements catty-cornered from each other make a pair and respective pairs of radiation elements are arranged +45 to −45 degrees with respect to verticality (or horizontality) and are used, for example, in transmitting (or receiving) the corresponding one of two linear polarizations, which are orthogonal to each other. Further, multiple radiation modules, each of which includes the four dipole-shaped radiation elements, are usually arranged vertically on the reflector so as to form one antenna array.
Further, an example of such a dual-band polarized antenna is disclosed in KR Patent Application No. 2000-7010785 (Title: “Dual-Polarized Dual-Band Antenna”, Filed Date: Sep. 28, 2000) first filed by Kathrein-Verke A G, or in KR Patent Application No. 2008-92963 (Title: “Dual-Polarized Dual-Band Antenna for a Mobile Communication Base Station”, Filed Date: Sep. 22, 2008) first filed by the present applicant.
In a multi-band antenna, multiple antennal arrays, according to each band, are installed on one reflector. For example, in order to implement a tri-band antenna, a total of three antenna arrays, one for each band, should be installed. In order to seek the best method for installing multiple antenna arrays as described above, an arrangement structure of an antenna array for each band, a structure of radiation modules constituting antenna arrays for each band, and an effect by mutual interference between antenna arrays for each band should be considered. At this time, the radiation performance of antenna arrays should be ensured while making the entire size of the antenna as small as possible. However, it is considerably difficult to design an antenna that satisfies such conditions in a limited space (on one reflector).
Therefore, various studies are currently being carried out on the more optimized structure of a multi-band multi-polarized antenna, the optimization of the size of an antenna, a stable radiation characteristic, the easy adjustment of beam width, an easy antenna design, etc.